The NFkB family of transcription factors plays a pivotal role in the regulation of inflammation and the development of the immune system. Abnormal alteration of the NFkB pathway has been implicated in cancer, dysfunction of the immune system, and perhaps aging. Recent evidence has shown that the post-translational modification of the NFkB members is involved in the activation of this pathway. The mechanism involved in the selective recruitment of the NFB members to the numerous possible NFkB- responsive genes is not been fully elucidated. We are interested in understanding the role of protein phosphorylation in the activation of transcription and the selectivity of gene expression. We have previously demonstrated that the phosphorylation of p65 at serine 536 was differentially recruited to selective promoters following cell activation. We have recently demonstrated that the distance between the site of p65 binding and the transcription start site of a particular gene determines if p65 needs to be phosphorylated on serine 536. The phosphorylation of p65 was not involved in the formation of an enhanceosome, where the recruitment of histone modifying enzymes to proximal promoters was required. These findings suggested that the phosphorylation of p65 and the cis-acting elements of the promoter regulate the various NFB genes. We are currently investigating the role of the various phosphorylation sites on p65 controls the chromatin architecture surrounding p65 responsive genes. We are also examining how the various IB members regulate the nuclear translocation of phosphorylated p65.